Optical switching systems designed to switch one or more optical elements (e.g., various lenses) into and out of an optical path are known and may be utilized in, for example, satellite applications. One relatively familiar type of optical switching system employs a processor, a motor, and a wheel mechanism having a plurality of optical elements disposed along its perimeter. The processor is coupled to the motor, which is, in turn, coupled to the wheel mechanism. An optical path passes through a portion of the wheel's perimeter such that the wheel may be rotated by the motor about the wheel's central axis to position a given optical element within the optical path. To move the optical element into the optical path, the processor first establishes the current rotational position of the wheel and subsequently determines the rotational adjustment required to move the desired optical element into the optical path. The processor then commands the motor to perform the required adjustment.
Unfortunately, in conventional optical switching systems of the type described above, the amount of time and energy required to move a newly selected optical element into the optical path may be undesirably high, especially when the newly selected optical element is disposed opposite the formally selected element, due to the sequential configuration of the optical elements around the perimeter of the wheel. Though the amount of time required for optical element switching may be improved by increasing the speed at which the wheel rotates, the rapid movement of the wheel may cause system disturbances (e.g., vibrations), which may blur the optical image and interfere with precise optical controls. To compensate for the disturbances that a rapidly moving wheel may cause, some systems provide for long settling periods after wheel movement; however, this solution involves undesirably long delays and is consequently less than ideal. Other known optical switching systems employ complex force compensation and/or isolation mechanisms to address system disturbances. However, such mechanisms increase system complexity and, in some cases, decrease system reliability.
To help mitigate the above-noted drawbacks, specialized optical element switch assemblies have been developed. Individual switch assemblies of this type may comprise a spring-biased pivot shaft coupled to an actuator arm having an optical element included thereon (e.g., coupled to one end thereof). The pivot shaft biases the actuator arm between first and second latched positions, which may position the optical element within and outside of the optical path, respectively. When the arm is held in one of the latched positions, the spring-biased pivot shaft exerts a rotational force on the arm in the direction of the other latched position. Thus, when released from a latched position at which it has been held, the actuator arm will swing under the influence of the pivot shaft toward the other latched position. Due to unavoidable system losses, the spring-biased pivot shaft will not provide enough energy to fully rotate the arm to the other latched position. Therefore, a latch mechanism is provided to help complete the arm's rotation and secure the arm at the other latched position against the force of spring-based pivot shaft. This mechanism may be mechanical, but is preferably magnetic. With reference to the later, a magnetic latch mechanism may comprise a permanent magnet configured to attract and physically engage a portion of the arm (e.g., a terminal end of the arm opposite the optical element), which may also be equipped with a magnet. This configuration is advantageous in that the arm may be held in a desired position for an indefinite period of time with little to no power consumption. To release the arm from a latched position, a control coil may be provided around a magnet disposed on the actuator arm or the magnet employed by the magnetic latch so as to form an electromagnet. When current is delivered to the coil, a magnetic field is generated counter to the field produced by the magnetic latch mechanism, and the actuator arm is released. The actuator arm then rotates under the force of the spring-biased pivot shaft toward the opposite latched position. A second magnetic latch mechanism, which again provides the additional energy required to fully rotate the arm, then physically engages the arm and secures it at the other latched position.
For the above described reasons, optical element switch assemblies employing spring-biased pivot shafts represent a considerable improvement over assemblies employing wheel-based mechanisms. However, even these improved assemblies present certain problems. For example, such assemblies may still produce physical disturbances when securing the actuator arm at a latched position. These disturbances occur because the field strength of the magnets employed by a magnetic latching mechanism must of a relatively high magnitude so as to overcome an opposing rotational force exerted on the arm by the pivot shaft in order to pull the actuator arm into a latched position resulting in significant impact between the arm and the switch assembly and, thus, a relatively high contact force being transmitted to the switch assembly upon actuator arm latching. This, in turn, results in unwanted shock and vibration throughout the switch assembly. Though secondary spring assemblies may be provided proximate either latched position to physically engage the actuator arm and oppose the force of the magnetic latch to soften the impact, these arrangements are complex, costly, and do not fully eliminate system disturbances.
In view of the above, it should be appreciated that it would be desirable to provide a switching assembly (e.g., of the type used to switch one or more optical elements into and out of an optical path) that minimizes system impact disturbances by employing a magnetic latching mechanism capable of securing a rotatable arm without physically contacting the actuator arm. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.